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              <h1>消息负载均衡策略 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
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        const quizData = [
  {
    "question": "在RocketMQ中，Producer端的默认队列选择策略是什么？它的主要特点是什么？",
    "options": [
      "哈希(Hash)策略，它能确保具有相同业务键的消息被发送到同一个队列，适用于顺序消息场景。",
      "随机(Random)策略，它完全随机地选择一个队列，以实现绝对的负载均衡。",
      "轮询(Round-Robin)策略，它简单高效，能确保消息在宏观上均匀分布到各个队列，但不考虑Broker的实时负载。",
      "延迟容错(Latency Fault Tolerance)策略，它会优先选择响应时间最短的Broker，是默认开启的高性能模式。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档明确指出，RocketMQ Producer默认采用轮询（Round-Robin）方式来选择消息队列。这种策略通过一个自增的索引对队列列表进行取模，从而依次选择下一个队列。它的优点是实现简单、分发均匀，但缺点是它不会感知后端Broker的健康状况或负载压力。",
    "source": "文档中「Producer端的负载均衡机制」-「1.1 默认队列选择策略」部分",
    "hint": "文档提到，在不启用延迟容错的情况下，Producer会通过一个自增的计数器来选择队列。"
  },
  {
    "question": "在什么样的业务场景下，使用自定义的`HashMessageQueueSelector`是必要的？",
    "options": [
      "当系统对消息发送的成功率要求极高，需要动态规避故障Broker时。",
      "当需要将消息发送到当前负载最低的Broker以实现最佳性能时。",
      "当需要保证同一类业务消息（例如同一个订单的创建、支付、完成消息）被消费者严格按顺序处理时。",
      "当系统部署在多个机房，希望优先向同机房的Broker发送消息以降低延迟时。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "为了保证消息的消费顺序，必须将需要保证顺序的一组消息发送到同一个MessageQueue中。`HashMessageQueueSelector`通过对业务键（如订单ID）进行哈希运算，并将结果对队列总数取模，来确保同一业务键的所有消息始终被路由到固定的队列，从而满足顺序消息的需求。",
    "source": "文档中「Producer端的负载均衡机制」-「1.3 自定义队列选择器」部分",
    "hint": "思考一下，要让消息被顺序消费，前提条件是什么？这组消息必须落在哪里？"
  },
  {
    "question": "当一个Consumer Group中的消费者实例频繁上线或下线时，为了最大限度地减少因Rebalance（重平衡）导致的队列重新分配，应该选择哪种队列分配策略？",
    "options": [
      "平均分配策略 (AllocateMessageQueueAveragely)",
      "一致性哈希分配策略 (AllocateMessageQueueConsistentHash)",
      "环形分配策略 (AllocateMessageQueueAveragelyByCircle)",
      "机房感知分配策略 (AllocateMessageQueueByMachineRoom)"
    ],
    "correctAnswerIndex": 1,
    "explanation": "一致性哈希算法的核心优势在于，当节点（此处指消费者）增加或减少时，它只会影响到哈希环上一小部分数据的映射关系，从而最小化需要迁移的队列。这使得它非常适合消费者数量经常变化的动态环境，可以减少重平衡带来的系统抖动。",
    "source": "文档中「Consumer端的负载均衡策略」-「2.3 一致性哈希分配策略」部分",
    "hint": "文档中有一种策略的特点是“减少重平衡时的队列迁移”。"
  },
  {
    "question": "关于RocketMQ Consumer的Rebalance（重平衡）机制，以下哪个描述是错误的？",
    "options": [
      "当Consumer Group中新增或移除消费者实例时会触发Rebalance。",
      "Rebalance的目的是为了将Topic下的所有队列尽可能均匀地重新分配给当前存活的消费者。",
      "Topic的队列数量发生变化（例如管理员增加了队列）也会触发Rebalance。",
      "Rebalance期间，消费者会继续处理当前持有的所有队列中的消息，直到消息处理完毕再接收新分配的队列。"
    ],
    "correctAnswerIndex": 3,
    "explanation": "在Rebalance流程中，消费者会“停止消费不再分配给自己的队列”，并“开始消费新分配的队列”。这意味着它不会等待旧队列的消息处理完毕，而是会立即释放对旧队列的所有权，并获取新队列的消费权。这是为了尽快完成重平衡过程，让整个消费组恢复正常工作。",
    "source": "文档中「Consumer端的负载均衡策略」-「3. 重平衡触发机制」部分",
    "hint": "查看重平衡流程的第4步和第5步，消费者是如何处理新旧队列的？"
  },
  {
    "question": "Producer端的延迟容错机制(Latency Fault Tolerance)是如何提高消息发送的可靠性的？",
    "options": [
      "它通过增加消息的副本数来确保即使一个Broker宕机，消息也不会丢失。",
      "它会记录近期发送失败或响应过慢的Broker，并在之后的一段时间内主动避开这些Broker，优先选择健康的节点。",
      "它强制要求消息必须同步写入Master和Slave节点成功后才返回确认，从而提高可靠性。",
      "它在发送失败后，会无限次地重试，直到消息发送成功为止。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "延迟容错机制通过一个内部的数据结构记录每个Broker的发送延迟和失败情况。在选择队列时，它会查询这个记录，如果一个Broker被标记为“不可用”（因为最近发送失败或延迟过高），Producer就会跳过该Broker上的所有队列，从而动态地规避故障节点，提高发送成功率和性能。",
    "source": "文档中「Producer端的负载均衡机制」-「1.2 延迟容错队列选择策略」部分",
    "hint": "该机制的特点之一是“动态感知Broker的可用性和响应时间”。"
  },
  {
    "question": "在一个跨多个数据中心部署的RocketMQ集群中，为了降低网络延迟和跨机房流量成本，应该为消费者配置哪种队列分配策略？",
    "options": [
      "平均分配策略 (AllocateMessageQueueAveragely)，因为它能保证每个机房的消费者负载最均衡。",
      "一致性哈希分配策略 (AllocateMessageQueueConsistentHash)，因为它能减少跨机房消费者上下线带来的影响。",
      "机房感知分配策略 (AllocateMessageQueueByMachineRoom)，因为它会优先为消费者分配其所在机房的Broker上的队列。",
      "环形分配策略 (AllocateMessageQueueAveragelyByCircle)，因为它轮流分配的特性可以打散机房的集中访问。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "机房感知分配策略的设计目标就是解决跨机房部署的问题。它会识别消费者和Broker所在的机房信息，在分配队列时，优先将同机房的队列分配给消费者。这极大地减少了不必要的跨机房网络调用，从而提升效率并降低成本。",
    "source": "文档中「Consumer端的负载均衡策略」-「2.4 机房感知分配策略」部分",
    "hint": "文档中专门有一种策略的特点是“支持跨机房部署场景”和“减少跨机房访问”。"
  },
  {
    "question": "在RocketMQ的Broker集群中，读写分离机制是如何实现读负载均衡的？",
    "options": [
      "Producer随机选择Master或Slave节点写入，Consumer也随机选择节点读取。",
      "所有读写请求都发往Master节点，Master再将读请求转发给负载较低的Slave节点。",
      "Producer只向Master节点写入数据，而Consumer可以从Master或Slave节点读取数据，从而分担Master的读取压力。",
      "NameServer会根据Broker的负载情况，动态地将部分Broker设置为只读模式，引导消费者访问。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "RocketMQ的读写分离是基于Master-Slave架构的。写操作具有高一致性要求，因此总是发生在Master节点。而读操作（消费）可以容忍轻微的延迟，因此可以配置消费者从Slave节点拉取消息。这样，大量的读请求就被分流到了Slave节点，减轻了Master节点的负载。",
    "source": "文档中「Broker集群的负载均衡实现」-「3. 读写分离机制」部分",
    "hint": "该机制下，Producer和Consumer的写入和读取目标节点是不同的。"
  },
  {
    "question": "根据文档中的最佳实践，对于一个消费者组和其订阅的Topic，消费者数量和队列数量之间应该保持什么样的关系？",
    "options": [
      "消费者数量必须严格等于队列数量，以达到一对一处理的最佳效率。",
      "消费者数量应远大于队列数量，以便在部分消费者宕机时有足够的备份。",
      "消费者数量不应超过队列数量，否则多出的消费者将无法分配到任何队列而处于空闲状态。",
      "消费者数量和队列数量之间没有特定关系，系统会自动进行平衡。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "在同一个消费组内，一个队列在同一时间只能被一个消费者实例消费。如果消费者数量超过了队列数量，那么多出来的消费者将因为无法分配到任何队列而变得空闲，造成资源浪费。因此，规划消费者实例数量时，其上限就是Topic的队列数量。",
    "source": "文档中「Consumer端的负载均衡策略」-「4. 负载均衡优化策略」部分",
    "hint": "思考一下，如果消费者比队列还多，多出来的消费者能分配到队列进行消费吗？"
  }
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        }

        function showResult(isCorrect, questionData) {
            resultContainerEl.innerHTML = ''; // 清空之前的结果
            const resultBox = document.createElement('div');
            resultBox.className = `result-box ${isCorrect ? 'correct' : 'incorrect'}`;
            
            let html = `<h3>${isCorrect ? '回答正确！' : '回答错误'}</h3>`;
            if (!isCorrect) {
                html += `<p><strong>正确答案是：</strong> ${questionData.options[questionData.correctAnswerIndex]}</p>`;
            }
            html += `<div class="explanation-text">${questionData.explanation}</div>`;
            html += `<div class="source-text">来源: ${questionData.source}</div>`;
            
            resultBox.innerHTML = html;
            resultContainerEl.appendChild(resultBox);

            // 禁用所有选项的点击事件，并高亮正确/错误答案
            Array.from(optionsListEl.children).forEach((child, index) => {
                child.style.pointerEvents = 'none';
                // 高亮正确答案
                if (index === questionData.correctAnswerIndex) {
                    child.classList.add('correct'); // 需要添加CSS样式
                    child.style.backgroundColor = '#d4edda';
                    child.style.borderColor = '#c3e6cb';
                }
                // 如果选错了，高亮错误选项
                if (!isCorrect && index === userAnswers[currentQuestionIndex]) {
                    child.classList.add('incorrect'); // 需要添加CSS样式
                    child.style.backgroundColor = '#f8d7da';
                    child.style.borderColor = '#f5c6cb';
                }
            });
        }

        function goToNextQuestion() {
            if (currentQuestionIndex < quizData.length - 1) {
                currentQuestionIndex++;
                loadQuestion();
            } else {
                showFinalScore();
            }
        }

        function goToPreviousQuestion() {
            if (currentQuestionIndex > 0) {
                currentQuestionIndex--;
                loadQuestion();
            }
        }
        
        function showHint() {
            const currentQuestion = quizData[currentQuestionIndex];
            if (currentQuestion.hint) {
                hintContainerEl.textContent = currentQuestion.hint;
                hintContainerEl.style.display = 'block';
            } else {
                hintContainerEl.style.display = 'none';
            }
        }

        function showFinalScore() {
            document.querySelector('.quiz-body').style.display = 'none';
            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  